====== Controlling the Electro-magnetic Buzzer ======

The CPi-A/B/C/S series panel PCSs have a built-in electro-magnetic buzzer. By default, it beeps when the screen is touched.

===== Enabling/Disabling the Touch Beep =====

To disable the touch beep, simply execute the following commands:
<code>
sudo systemctl stop touch-beep.service
sudo systemctl disable touch-beep.service
</code>


To enable the touch beep, simply execute the following commands:
<code>
sudo systemctl enable touch-beep.service
sudo systemctl start touch-beep.service
</code>

===== Programming the Electro-magnetic Buzzer =====

The electro-magnetic buzzer is tied to GPIO pin 30 on the CPi-A and CPi-B panel PCs and GPIO pin 27 on the CPi-C panel PCs.  One way to program it is to use the [[https://abyz.co.uk/rpi/pigpio/|pigpio library]].  The following examples illustrate how to use a programming language to play a beep.

==== C++ Example ====

<code C++>
#include <pigpiod_if2.h>
#include <thread>

using namespace std;

#define PIN 30  //  CPi-A/B/S
//#define PIN 27  //  CPi-C

int main()
{
   auto instance = pigpio_start(NULL, NULL);

   // We actually can't achieve 2700Hz due to the sampling
   // rate, but it will do the best it can
   set_PWM_frequency(instance, PIN, 2700);

   // 128/255 = 50% duty
   set_PWM_dutycycle(instance, PIN, 128);

   // play beep for 100 milliseconds
   this_thread::sleep_for(chrono::milliseconds(100));

   // turn off beep
   set_PWM_dutycycle(instance, PIN, 0);
   
   pigpio_stop(instance);
   
   return 0;
}
</code>

Compile with:
<code>
g++ playbeep.cpp -lpigpiod_if2 -o playbeep
</code>
==== Python Example ====

<code python>
import time
import pigpio

PIN = 30  # CPi-A/B/S
# PIN = 27  # CPi-C

pi = pigpio.pi()

# We actually can't achieve 2700Hz due to the sampling
# rate, but it will do the best it can
pi.set_PWM_frequency(PIN, 2700)

# 128/255 = 50% duty
pi.set_PWM_dutycycle(PIN, 128)

# play beep for 100 milliseconds
time.sleep(0.100)

#turn off beep
pi.set_PWM_dutycycle(PIN, 0)

pi.stop()

</code>

[[comfilepi:index|ComfilePi - Industrial Raspberry Pi Panel PC]]